With Forefront Threat Management Gateway (TMG) 2010 now discontinued, we sought a suitable reverse proxy solution that works with Lync Server and also supports other Microsoft products, such as Exchange and SharePoint. With the release of Windows Server 2008, it is now possible to add an optional component called IIS Application Request Routing (ARR) 2.5 to the Internet Information Services (IIS) role. This component enables IIS to handle reverse proxy requests, URL rewrites, and load balancing, among other features.
Read more at source: http://blogs.technet.com/b/nexthop/archive/2013/02/19/using-iis-arr-as-a-reverse-proxy-for-lync-server-2013.aspx